1. Field of the Invention
The invention pertains to a working device according to the preamble of patent claim 1 that contains an internal combustion engine, and to a method of monitoring an oil level in a combustion engine according to the preamble of patent claim 24.
2. Description of the Related Art
Internal combustion engines, in particular four-cylinder gas or diesel engines, require a sufficient supply of oil in order for the lubrication to function properly. This oil supply is provided by oil contained in an oil reservoir. The oil reservoir is usually located in the vicinity of a crankcase so that the oil is distributed to the points of lubrication of the cylinders, pistons, bearings, etc. through sling lubrication, or by means of an additional oil pump.
In such systems, the presence of an amount of oil required for engine lubrication is verified using an oil dipstick, for example, or using various sensors (e.g. oil pressure switches in the case of lubrication using oil pumps). The sensors can be used in a monitoring circuit such that they shut off the engine if a lack of oil is detected, or such that they indicate the lack of oil via control lamps or similar devices. Engines without oil pumps usually have dipsticks or sight glasses.
Simple equipment for the purpose of oil monitoring also consist of a float that measures the oil level wherein the ignition system of the internal combustion engine is interrupted when there is a lack of oil. In this case, the engine does not start at all with a low oil level. For high-vibration machines and uncontrolled turbulent oil motion in the engine, the engine can also shut off even if there is sufficient oil present. Since the oil is tossed around, the float assumes a position that represents a lack of oil such that the corresponding actions are taken and the engine is shut off.
Since the known monitoring systems prevent the internal combustion engine from starting at all when a low oil level is determined—as illustrated above—, the operator of the equipment cannot know why the engine will not start. Consequently, he may take inappropriate or unnecessary actions to return the equipment to operation (replacement of spark plugs, cleaning the carburetor, etc.).
Many working devices include an internal combustion engine as well as a vibration exciter that is driven by the internal combustion engine. Possible working devices include: tampers for soil compaction, vibration plates, hammers, etc. Based on the strong vibration produced by the vibration exciter, the oil in the internal combustion engine is heavily circulated. Accordingly, it is difficult to determine, using known oil monitoring systems, whether enough oil is available for lubrication of the internal combustion engine.
In U.S. Pat. No. 6,560,366 B1, a system to determine the chemical modification of oil in an automobile is described. One element of the system is an oil level measurement device. Based on the change in the amount of oil, the change in the chemical composition of the oil is determined. In order to attain the required measurement precision, the oil amount is determined prior to the start of the machine using an oil measurement sensor.
From U.S. Pat. No. 4,306,525, an oil display is known in which a visual oil sensor is provided at an oil recycle line in an internal combustion engine. The measurement and display of the oil level is determined immediately after closing a key-operated switch, i.e. prior to starting the internal combustion engine.